Taming the Dichalcogenides: Isolation, Characterization, and Reactivity of Elusive Perselenide, Persulfide, Thioselenide, and Selenosulfide Anions

Abstract

Reactive sulfur species (RSS) and reactive selenium species (RSeS) play integral roles in hydrogen sulfide (H2S) and hydrogen selenide (H2Se) biological signaling pathways, and dichalcogenide anions are proposed transient intermediates that facilitate a variety of biochemical transformations. Herein we report the selective synthesis, isolation, spectroscopic and structural characterization, and fundamental reactivity of persulfide (RSS–), perselenide (RSeSe–), thioselenide (RSSe–), and selenosulfide (RSeS–) anions. The isolated chalcogenides do not rely on steric protection for stability and have steric profiles analogous to cysteine (Cys). Simple reduction of S8 or Se by potassium benzyl thiolate (KSBn) or selenolate (KSeBn) in the presence of 18-crown-6 afforded [K(18-crown-6)][BnSS] (1), [K(18-crown-6)][BnSeSe] (2), [K(18-crown-6][BnSSe] (3), and [K(18-crown-6][BnSeS] (4). The chemical structure of each dichalcogenide was confirmed by X-ray crystallography and solution-state 1H, 13C, and 77Se NMR spectroscopy. To advance our understanding of the reactivity of these species, we demonstrated that reduction of 1–4 by PPh3 readily generates EPPh3 (E: S, Se), and reduction of 1, 3, and 4 by DTT readily produces HE–/H2E. Furthermore, 1–4 react with CN– to produce ECN–, which is consistent with the detoxifying effects of dichalcogenide intermediates in the Rhodanese enzyme. Taken together, this work provides new insights into the inherent structural and reactivity characteristics of dichalcogenides relevant to biology and advances our understanding of the fundamental properties of these reactive anions.

Generation and Reactivity of Polychalcogenide Chains in Binuclear Cobalt(II) Complexes

“…Reaction of cyanide (CN – ) with elemental (neutral) sulfur to generate thiocyanate (SCN – ) has implications in biology in the context of cyanide detoxification. − Reactions of elemental sulfur and polysulfide, organopolychalcogenides, and transition metal–polysulfido complexes , with CN – have also been reported in the literature. The mechanism for the reaction of elemental sulfur and polysulfide with CN – has been studied very recently which suggested intramolecular cyclization to be the most favorable decomposition pathway for long chain polysulfides, while a mixture of unimolecular decomposition, nucleophilic attack, and scrambling pathways was proposed to be operative in the case of short chain polysulfides .…”

Reduction of nitrite to nitric oxide and generation of reactive chalcogen species by mononuclear Fe(ii) and Zn(ii) complexes of thiolate and selenolate

“…83,117,139 Very recently, Pluth and coworkers have reported the synthesis (by the reaction of thiolates and elemental sulfur/grey selenium), characterization, and fundamental reactivity (involving dithiothreitol, PPh 3 and CN − ) of persulfide (RSS − ), perselenide (RSeSe − ), thioselenide (RSSe − ), and selenosulfide (RSeS − ) anions. 140…”

“…This result, however, is somewhat in contrast with the recent report by Pluth and coworkers on the synthesis of perselenide (RSeSe − ) and thioselenide (RSSe − ), by the reaction of [Se] with PhCH 2 Se − and PhCH 2 S − , respectively. 140 The reactions involved in the generation of the reactive sulfur/selenium species also generated disulfides (5–18%)/diselenides (24–34%) and reactive sulfur/selenium species of different chain lengths (3–13%) and information regarding the same are provided in Table S9 †…”

Activity-Based Fluorescent Probes for Hydrogen Sulfide and Related Reactive Sulfur Species

“…This persulfide can then undergo an intramolecular nucleophilic attack on the proximal ester to generate a 5-membered ring transition state and extrude the fluorophore and benzodithiolone as a byproduct. This general approach has also been applied to symmetric disulfides ( vide infra ) as well as to other hetero- and homodichalcogenides, all of which generate anionic and highly nucleophilic dichalcogenide intermediates . Importantly, disulfide reduction by H 2 S i generates a persulfide intermediate that is required for the subsequent intramolecular cyclization and fluorophore release.…”